|William Ayerst||31/10/2020 09:02:50|
66 forum posts
Thank you for the ideas of making one - that sounds like an amazing project for a bit down th eline.
In the meantime I've managed to win an original-manufacture Myford ratcheting toolpost on the auction site (why do we call it that instead of the name?)
I guess if I can find 3/8" tools they should in theory be bang on? if not then 8mm + about 1.5mm shimming is required.I've not got a grinding bench but I will ask father christmas for one, so for now I'll need to buy some tools which are pre-formed - then I can make my own tools!
5569 forum posts
I doubt it. Why would they be? It would be daft to design it so they were since the grinding process would always drop the tip a little so needing shims anyway.
6461 forum posts
No, shimming is almost always necessary.
The essential requirement of a shank is it puts the cutting edge near level with the lathe's spinning axis. Even slightly high is bad because the tool rubs. Too low is tolerable but most tools cut best positioned a little below the centre point. Tool points have to be adjustable. Shimming is the easy way of adjusting height. I use aluminium strip, cut up can metal, metal binding tape, and mild steel milled to height. Almost any metal will do. Easy but potentially time-consuming, so there are alternatives,
Shank size may not matter much provided the cutting edge can be put on target. Avoid oversized shanks because they either won't fit the tool-post and/or need a lot of grinding down: far more practical to use smaller shanks and shim them up to height.
Full sized shanks (3/8" on the ML7) are stiff and strong, but it's often advantageous to use smaller shanks for fine work or cutting in tight spaces. My lathe takes 12mm tools, but I prefer 10mm, use 8mm a fair bit, and 6mm on special occasions. Decided by the job - I don't use 12mm on small diameters and I don't use 6mm tools to rough out big lumps of steel. 8mm would be a good general-purpose size for a ML7.
Not used one myself, but boat type adjustable height holders are widely despised because they're fiddly and prone to move. Pretty much obsolete. Far more successful are the quick change types where the tool is held in an adjustable plug-in cartridge. Easy to set the tool height, the cartridge is solid, and no further adjustment is needed until the tool is resharpened.
A disadvantage of HSS is tool height is altered by sharpening, making re-shimming and readjustment necessary. It's all part of the game.
Setting tools to height isn't difficult, but it takes time. Industry favour carbide inserts, which are swapped out rather than sharpened - really quick with auto-tool changers. QCTP are probably the fastest way of swapping HSS tools, but I find a 4-way tool-post with pre-shimmed carbide insert tools fast enough for my purposes. Basically, once the tool-height needed by a particular set of insert holders is identified, the necessary shims can be ready to hand, glued together if the fancy takes me.
A huge amount depends on what the lathe is used for. Previous owners of William's ML7 didn't bother to hange the basic fitting it came with. Presumably the lathe was worked slowly with a limited range of tools. This might be fine for William too. Others have to work quickly on jobs requiring multiple tool-changes, or perhaps work best when they don't have their flow interrupted by fiddly tool-changing. For them a QTCP is best choice. In the middle is the 4-way tool-post. Up to 4 tools pre-mounted, with moderately fast tool changing provided the tools are pre-shimmed.
If I were William I wouldn't rush to change the holder. It will cut metal as well as any other! After the lathe has been used for a few projects it will be obvious to William if the holder needs to be changed or not. Could be the money is better spent on something else, and that list is endless...
Edited By SillyOldDuffer on 31/10/2020 10:42:05
|453 forum posts|
My toolpost is a after the Pratt-Bernerd QCTP which I thought had ridgeitity problems.Easy to make and I find it far quicker than my Dickson clone.The tool cartridges sit on the topslide with no overhang.The only drawback is one has to shim the tools to height,but once done it only needs checking after a resharpen.I can't show the image as the image occupies to much space on the post.So to view it is in my albums.
|William Ayerst||31/10/2020 13:20:26|
66 forum posts
Of course, I keep forgetting I'll in a position to grind my own tools! Is there any recommendation for a grinder, or is it relatively unimportant? A buffing wheel would be nice?
|Clive Brown 1||31/10/2020 15:09:26|
|537 forum posts|
If on a tightish budget, Screwfix do a 150mm d/e bench grinder for <£20. Won't be the best but you can't go too far wrong at that price. I rarely use the coarse wheel, so I could see it being replaced with a buffing wheel, but they tend to be more power hungry than a grinding wheel, so a more powerful machine might be better than the Screwfix lightweight.
|370 forum posts|
Many moons ago, some fora were a bit squiffy about EBAY and AMAZON and forbade their mention.
|John Baron||31/10/2020 16:24:47|
339 forum posts
You can get a cheap double ended grinder for £20 at various places, these are fine for HSS tool grinding but way under powered if you want to use it for buffing. Most of the buffing machines I've seen use 1Hp plus, and that is a small one.
|John Baron||31/10/2020 16:50:08|
339 forum posts
Hi William, Guys,
Here is a drawing of the tool block for the Norman patent tool post.
It is quite straight forward to make, though there is a bit of a technique when it comes to the split collet used to clamp the tool block to the post.
I've more if you want it ! I've now made several !
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